The invention relates to apparatus for mounting rotary devices, such as flywheels and the like, which are susceptible to critical vibratory effects caused by high speed operation. In particular, the present mounting structure reduces vibration caused by both internal and external factors, reduces the critical speed of the rotary device, reduces shock, attenuates torsional vibration, and substantially reduces gyroscopic bearing loads and reaction forces. The present structure allows a flywheel to precess slowly in the event of accidental angular displacement of the axis of rotation of the flywheel, thereby preventing damage to the flywheel or its associated bearing from excessive gyroscopic loading. Further, the present structure allows a flywheel to expand during rotation without excessive stress or strain at the interface between the flywheel and the shaft/hub assembly.
Rotary devices such as flywheels, gyroscopes, and the like have been known to man for centuries. Flywheels in particular have come to be used as a means for storing energy, the energy storage ability of a flywheel being generally increased as the square of the rotational speed. Flywheels capable of storing useful amounts of energy must therefore be capable of rotation at extremely high speeds. At such speeds, natural frequencies induce internal vibrations detrimental to the structural integrity of the flywheel. Further, externally-induced vibratory effects and shocks are magnified in effect by virtue of the high rotational speeds of these inertial devices. In addition to the foregoing problems, the use of high energy flywheels in vehicular applications usually require bulky gimbal structures which act to relieve gyroscopic loading should accidental angular displacement of the flywheel occur. The prior art has not found solutions to these and associated problems. Andrews in U.S. Pat. No. 3,537,332, provides a flywheel mounted on and rotatably coupled to a capstan in a manner such that the flywheel is free to seek a plane of rotation perpendicular to its dynamic axis. Andrews places compliant means such as rubber washers between the flywheel and at least one hub plate to provide a frictional coupling therebetween. Since the hub plate is attached to the capstan, the elastically mounted flywheel is caused to rotate on rotation of the capstan. The disclosure, teachings, and intended use of the Andrews structure requires that said structure be configured as described and shown in the aforesaid patent, i.e., the capstan extends through the flywheel to engage and attach to a hub plate which supports the flywheel against gravity. The structure thus provided cannot function to allow precession of a flywheel relative to a shaft such as would be necessitated by gross angular displacement of the axis of rotation of an inertial energy storage device. For example, accidental "rollover" of a moving vehicle employing a high speed flywheel as a prime energy storage source would produce gyroscopic loading forces which would cause damage to the flywheel and/or bearings unless fitted with external gimbal mountings or with the present invention. By virtue of the structure of the hub plate and washer arrangement of Andrews, the flywheel cannot precess more than a fraction of a degree about the capstan.
The present invention in the several embodiments thereof takes the general form of an elastic joint having a shaft mounted centrally thereto, the joint being further mounted centrally on a planar surface of a solid disc flywheel or either within or surmounting a central aperture in a rim flywheel. The present elastic joint is thus not limited to use with flywheel structures having a shaft extending through said structure. As will be described hereinafter, the present apparatus is equally useful for solid disc-type flywheels wherein the elastic joint of the invention is attached to either the upper or lower planar face of the flywheel or both. The elastic joint can be integrally formed into a rim-type flywheel as a centermost segment thereof, the shaft being mounted centrally through the joint. Alternatively, the elastic joint can be attached to a flywheel of any type at the center thereof either directly to the rotor portion thereof or to the central portion of a hub member holding the rotor.
In operation, the present elastic joint acts to reduce the critical speed of the flywheel to a level well below the operating speed range of the flywheel. Of equal significance is the ability of the present joint to attenuate flywheel-induced vibration such that the operating RPM range is above the natural frequency of the apparatus. Additionally, both externally-induced vibration, such as would be caused in a moving vehicle in which a flywheel was mounted, and torsional vibration, such as occurring with an associated electric or hydraulic motor, are attenuated through use of the elastic joint. Shock effects to the flywheel from external inputs are also reduced through use of the invention.
Accordingly, it is an object of the invention to provide an elastic hub mounting between a flywheel and a rotary shaft, which hub mounting couples the flywheel to the shaft for rotary movement and allows precession of the flywheel without the use of external gimbal mountings.
It is a further object of the invention to provide an elastic member coupling a flywheel to a shaft for rotary movement, the elastic member either joining a hub member carrying the flywheel rotor to the shaft or directly coupling the flywheel rotor to the shaft.
It is another object of the invention to provide an elastic gimbal mounting structure which allows precession of a flywheel relative to a stationary shaft while reducing vibratory and shock effects on the flywheel.
Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments thereof.